The present invention relates generally to digital content, and more particularly to techniques for embedding information into digital content, such as watermarks.
Conventional audio, video and multimedia content distribution and storage is largely based today upon digital technologies. In accordance with these technologies, audio-only, video-only, combinations of these, as well as text, still images, and so forth are encoded by bit streams that may be created, manipulated, separated, combined, stored, disseminated and played in a wide range of contexts. These contexts include, for example, broadcast for television viewing, over airwaves, satellite links, cable links, and so forth, as well as storage on recording media, such as physical and solid state memory.
In certain of these techniques, it has become increasingly important to embed certain types of data that does not, itself, represent the content. That is, certain bits in bit streams may represent the audio, video or similar content that is reproduced for the audience, while other code may provide information relating to the content. One type of data, for example, may include watermarks. Digital watermarks are defined by code which may be transmitted, stored, and remain resident with the code defining the underlying content, and that may be read or extracted when desired. Uses for such watermarks include, for example, tracking of content, identification of particular content, policing content for piracy, referencing and identifying content for the provision of additional content, products and/or services, and so forth. The watermarks themselves may simply be identifying code, or may transmit data or metadata relating to the content itself, such as for identifying the content, identifying particular portions of the content, and so forth. More generally, however, such embedded supplementary code may serve any of a range of purposes, that may relate directly to the content or to other functions, such as instructions, information, program updates, and so forth.
Known techniques for embedding watermarks and similar code into digital content have traditionally been limited to the use of a single channel. That is, the content may be stored and transmitted as a single channel of data. In such cases, the embedded code is simply stored in the single data stream. However, even where multiple channels are utilized, watermarks are typically stored in only one of these channels. While in most cases this may be sufficient, the amount of the data stream which can be allocated to the embedded data is typically quite limited, limiting in turn, the ultimate payload of the embedded data. There is a need, in the field, for improved techniques for embedding data, such as watermarks, into digital content.